Side rails are commonly used for tensioning and supporting screens in a screen deck. The side rails are removably attached to upright side walls or panels in the deck in a manner such that the rails engage a screen at its side edges and tension the screen in a secure manner.
Multiple vibrating screens are normally used, with a top screen separating the largest size of material, such as sand, gravel, crushed stone and the like, with the material which passes through the top screen falling onto an intermediate screen. The intermediate screen separates an intermediate size of material, with the remainder falling through the intermediate screen onto a finer screen, which in turn separates the larger particles of those falling onto it and the smallest size falling through for collection beneath.
Different techniques have been utilized to removably attach the screen rails to the side walls or panels. For example, one very common technique involves the use of bolts or pins which extend through apertures in the screen rails and corresponding apertures in the side walls. A fastener is then used to secure the bolt or pin in place. The bolt or pin head is thus located on the side of screen rail which is exposed to the rock being screened or sorted.
The entire screen deck assembly is then vibrated, usually to produce a slow forward movement and a rapid rearward movement, so that the rock material will move forward with the screen but, due to inertia will permit the screen to move rearwardly under it. As a result, the rock material will work its way forwardly on the respective screen, so that material which does not fall through the screen will be discharged from the front end of the respective screen, for collection.
In order to remove a screen, it has heretofore been necessary to remove the nut from each bolt outside the wall or panel and then reach inside the assembly to pull the bolts out of the side rail. After the old screen has been replaced by a new screen, it is necessary to insert each bolt, from the inside, through a hole in the screen rail and then through the hole in the side wall or panel, after which the nut may be replaced and tightened. As will be evident, since the side walls or panels prevent access to, and any view of, the side rail, from the outside of the panel, little help from someone on the outside of the panel may be obtained, except to place the washer and nut on the threaded end of the bolt, after it has been pushed through the hole in the side panel. The removal of the bolts, as well as replacing them, adds to the time consumed and the expense of changing a side rail or screen.
A similar procedure, of course, is used when using pins instead of threaded bolts. The pins include an elongated slotted aperture into which a wedge-shaped retainer is driven to tension the pin after it has been inserted through registering holes or openings in the screen rail and the side wall or panel.
Metal side rails for tensioning vibrating screens are subject to undue wear, thus requiring relatively frequent replacement. A layer of rubber may be molded onto the side rail, above a flange which receives a side strip attached to the screen, as by welding, and has a hook which engages the flange. Such a layer increases the useful life of the side rail considerably.
One technique which has been previously proposed for attaching side rails to avoid the problems discussed above involved the use of an anchor on the side of the rail facing the side wall and a bolt or pin having a hook at one end. The hook is intended to engage the anchor when the bolt or pin is inserted through an opening or aperture in the side rail and then rotated. This technique requires the use of special bolts or pins and has not been widely accepted. Also, it is not easy for the workman to determine with certainty whether the bolt or pin is properly positioned to engage the side rail.
Another problem associated with changing of screens in a screen deck is that it is necessary to completely remove the side rails from the deck after they have been loosened. This requires additional time and work.
There has not heretofore been provided an effective, safe and efficient mounting system for removably attaching side rails to side walls or panels of a screen deck using conventional bolts and pins.